Switch pile-ups

ABSTRACT

A molded plastic insulator for use in switch pileups, has a plurality of arcuate, self-locking peripheral recesses and projections alternately surrounding the apertures formed therein. The number and orientation of the recesses and projections are chosen in such a manner that even when they surround two or more apertures, the insulators are symmetrical from an interlocking standpoint when stacked.

United States Patent [72] Inventors James D. Brandlein;

3/1942 Livingston.

2/1956 .lonsson..... 7/1960 Hufnagal...

6/1961 Dumkeetal g M l 6 9 l 5 l 2 6 8 2 2,254,720 9/1941 Wilcox...... Joseph D. Mathis, lndianapol's, lnd. 2,277,443 [21] AppLNo. 815,710 2,382,520 8/1945 Tinnennan [22] Filed Apr. 14,1969 2,395,300 2/l946 Slauson..... [45] Patented Apr. 6, 1971 2,734,257 [73] Assignee Western ElectricCompanyJncorporated 2,945,107

New York, N.Y.

Primary Examiner-11. 0. Jones Attorney H. J Winegar, R. P. Miller and A. C.

[54] SWITCH FILE-UPS 6 Claims, 8 Drawing Figs.

Schwartz, J r.

ABSTRACT: A molded plastic insulator for use in switch 2\h MM min m mF mm pileups, has a plurality of arcuate, self-locking peripheral 166-1, 168 29/630 recesses and projections alternately surrounding the apertures formed therein. The number and orientation of the recesses and projections are chosen in such a manner that even when they surround two or more apertures, the insulators are symmetrical from an interlocking standpoint when stacked.

2 Sm m N" WM MAW mm" "m a RmG H1 mm W Qvvvs PATENTEU APR 6197i SHEET 1 (IF 2 \NVENTORS J. D. BR NDLEIN B .J.D.MATH\S av gw ATTORNEY PATENTED APR 6 IBYI SHEET 2 OF 2 swrrcu PILE-UPS BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to electrical insulators and, more particularly, to those employed in electrical switch pileups.

2. Description of the Prior Art Heretofore, insulators employed in electrical switch pileups have generally been blanked out of fiber sheet stock, and then apertured to accommodate one or more fastening members, such as threaded bolts. Insulators thus formed necessarily have had planar surfaces and, as a result, have in no way pro vided isolation of the peripheral walls defining the apertures in the switch contacts from the fastening members. Accordingly, it has been necessary heretofore in such switch pileups to utilize an insulating bushing or sleeve to surround the fastening member and thereby isolate it from the switch contacts. Because of having planar surfaces, the insulators also could not be nested or stacked in interlocking relationship so as to facilitate their alignment during the assembly of a switch pileup.

Fiber insulators also have several other disadvantages when used in applications such as switch pileups. More specifically, they are not immune to many chemicals and are capable of absorbing moisture. Fiber insulators also do not lend themselves to color coding, which is often desired when there are peculiar spacing variations required in certain switch pileups, or in cases where there are a number of coded switch pileups, with the insulators varying only slightly in their cross-sectional dimensions. Further, as fiber insulators are blanked out of sheet stock, and as the apertures are formed therein by a punch and die operation, there is often considerable waste of raw material in the manufacture of such insulators.

In an effort to obviate a number of the disadvantages associated with the use offiber insulators heretofore, attention was directed to the use of molded plastic insulators. Such insulators are conducive to color coding, reduce material waste, are immune to most chemicals and do not absorb moisture. They have often been constructed with circular or annulus type protuberances on one side and mating recesses on the opposite side of the insulator so as to facilitate the nesting thereof when stacked to form a pileup. The recesses and projections have also been dimensioned so as to effectively insulate the peripheral walls defining the apertures of the switch contacts from the fastening members, without requiring a separate insulating bushing or sleeve associated with each fastening member.

Such prior plastic formed insulators, however, have had the disadvantage that they are not symmetrical from an interlocking standpoint, i.e., each successive insulator requires a particular side up relative to the preceding one in the stack in order to have each circular or annulus-type projection nest in the recess of the preceding insulator.

Moreover, such insulators do not prevent relative angular rotation therebetween when constructed with only one aperture.

SUMMARY OF THE INVENTION An object of this invention is to provide a new and improved insulator of the type applicable for use in switch pileups, wherein the insulator is symmetrical from and interlocking standpoint.

Another object of this invention is to provide new and improved interlocking insulators which inherently insulate metal fasteners from switch contacts when used in switch pileups, are immune to most chemicals and moisture, and are conducive to color coding.

A further object of this invention is to provide new and improved insulators which can be stacked in interlocking relationship, and interleaved with switch contacts in a switch pileup in such a way that the need of insulating bushings or sleeves associated with the fasteners is obviated.

In accordance with the invention, insulators for use in switch pileups are molded out of plastic material, with a plurality of self-locking recesses and projections alternately surrounding the apertures formed therein. These recesses and projections may take a number of forms, such as holes and studs, arcuate segments, etc.

The number and orientation of the recesses and projections are chosen in such a manner that even when they surround two or more apertures, the insulators are symmetrical from an interlocking standpoint. This is a significant feature not only when stacking switch contacts and insulators in an interleaved manner manually, but also when it is desired to feed the insulators to an assembly station on an automated basis for high volume production.

By being made of plastic material, the insulators are not only immune to most chemicals, as well as to absorbing moisture, but they are conducive to color coding. Further, by reason of the interlocking recesses and projections, the insulators inherently facilitate alignment and obviate the need for insulating bushings or sleeves to isolate the metal fasteners from the switch contacts in a switch pileup.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a perspective view of a molded plastic insulator for use in switch pileups embodying the principles of the present invention;

FIG. 2 is a plan view of the insulator of FIG. 1;

FIG. 3 is a cross-sectional view taken along the line 3-3 of FIG. 2 of the insulator depicted in FIG. 1;

FIG. 4 is a fragmentary, partially exploded perspective view of an almost completely assembled switch pileup incorporating molded plastic insulators of the type embodied in the present invention;

FIG. 5 is a perspective view of a second insulator embodiment, and also illustrates in phantom a fixture applicable for stacking an interleaved array of switch contacts and insulators constructed in accordance with the second embodiment;

FIG. 6 is a plan view of the molded plastic insulator depicted in FIG. 5;

FIG. 7 is a cross-sectional view taken along the line 7-7 of FIG. 6 of the insulator depicted in FIG. 5; and

FIG. 8 is a plan view of a third insulator embodiment incorporating the principles of the present invention.

DETAILED DESCRIPTION With particular reference first to the embodiment depicted in FIGS. 1-4, an insulator 10 of unique construction is employed in the fabrication of a switch pileup 11, shown only partially fabricated in a fragmentary exploded view in FIG. 4. The switch pileup 11 comprises an interleaved stack of insulators I0 and conductive switch contacts 13 secured to a main support frame 17 by means of two threaded screw-type fasteners I9, which mutually engage the threads in aligned tapped holes 21 of the frame 17. Another tapped hole 22, which may comprise only one of several, is employed to subsequently secure the frame 17 with the switch pileup 11 secured thereto to other associated apparatus which is of no concern with respect to the instant invention.

It is to be understood, of course, that the frame 17 and switch contacts I3 may be of varied configurations, the particular ones disclosed being intended for purposes of illustration only. Similarly, the number of screw fasteners 19 employed to secure the switch pileup to the frame need not necessarily comprise two, but rather, in many applications may comprise either one or a number of the same or similar fasteners.

In accordance with the principles of the present invention, the insulators 10 of the switch pileup are each molded out of a suitable plastic material, such as Lexan, which exhibits desirable cold-flow characteristics. Each insulator has a number of apertures 23 therein, two being shown in the particular illustrative embodiment. A plurality of segments, in the form of self-locking arcuate recesses 25 and projections 27, are alternately and circumferentially disposed about each of the apertures 23. In the embodiment of FIG. 1, each arcuate recess 25 on one side of the insulator l coincides with an arcuate projection 27 on the opposite side of the insulator.

In addition, the peripheral recesses 25 and projections 27 on the same side of the insulator are circumferentially disposed about each associated aperture such that a projection 27 is diametrically disposed with respect to a recess 25. Further, the location of the recesses and projections are reversed with respect to the two apertures, as is best visualized by comparing the location of the recesses and apertures relative to an imaginary X axis drawn through the centers of the two apertures.

As is also best seen in FIG. 2, the recesses 25 are of slightly greater width than the projections 27 so that the former can readily accommodate the latter when two adjacent insulators are stacked in a switch pileup with a switch contact interposed therebetween. The thickness of the projections 27, Le, the distance they protrude outwardly from the planar surfaces of the insulator and, conversely, the depth of the mating recesses 25, will depend primarily on the thickness of the switch contacts being employed. It is obvious, of course, that the depth of the recesses and the outward extension of the projections 27 as best seen in FIG. 3, must be sufficient to effect an interlocking relationship between adjacent insulators after a switch contact has been interposed therebetween.

With respect to the top and bottom insulators of a given switch pileup, such as those designated 10a and 10b, respectively, in FIG. 4, they may be molded to have recesses and projections on only one planar side so that the underside of the head of the fasteners 19 and the mating surfaces of the frame 17 would be flush with the respective adjacent surfaces of these insulators.

Alternatively, by molding the insulators out of a suitable deformable plastic material, and by initially forming the projections thereon so as to have smaller outward extensions than the depths of the recesses, the projections adjacent the underside of the head of the fasteners and adjacent the mating surfaces of the frame could be readily compressed into those portions of the aligned recesses of the same insulators not occupied by nesting projections from the adjacent insulators.

In any event, it normally would be desirous that no projections act as spacers, as they could possibly adversely affect the attainment of reliable and permanent compressive engagement of all members of the switch pileup after the screw-type fasteners had been turned down.

As thus constructed, the insulator l0 embodied herein is symmetrical from an interlocking standpoint, which allows a succession of such insulators to be interleaved with a succession of switch contacts to form a switch pileup regardless of the individual orientation of a given insulator, as long as the apertures therein are in alignment with the preceding insulator and/or switch contacts. This is a very important feature in that it greatly facilitates the use of automated techniques for feeding the insulators and switch pileups to a common assembly station for stacking. Moreover, such an automated system is highly advantageous because of the very small dimensions of the switch contacts and insulators in many switch pileups, these members often being less than flinch in the longest dimension in many cases.

The insulator 10 as embodied herein also exhibits a number of other important and beneficial advantages over prior fiber insulators. For example, the present insulators, by being made of appropriate plastic, such as Lexan, Nylon, etc., are not susceptible to moisture or to most chemicals. The present insulators, by reason of their nesting relationship when stacked, also obviate the need for insulating bushings which were required heretofore with conventional, apertured fiber insulators having planar surfaces. The insulators 10 in being molded, also minimize material waste during manufacture. Finally, the insulators by being made out of plastic may easily be colorcoded to identified variations in thickness and/or other characteristics thereof, such as with respect to identifying the top and bottom insulators which normally would have recesses and projections associated with only one major side thereof, for the reasons noted above. It would also be desirous, of course, to color-code the insulators according to cross-sectional dimensions so as to be able to readily identify which insulators were applicable for use with a given coded switch pileup.

In the embodiments depicted in FIGS. 1-4, as well as in other similar arrangements wherein an odd-number of recesses and projections respectively are circumferentially disposed about a given aperture in the insulator, it appears that several conditions are required in order to insure interlocking symmetry, regardless of orientation of the insulator, whenever two or more interlocking apertures are to be formed therein.

First, the recesses 25 and projections 27 must be in altemate relationship as circumferentially disposed on a given side of and about each aperture. Secondly, each recess must be diametrically disposed with respect to a projection on the same side of the insulator. Thirdly, the pattern of recesses and projections must be reversed in adjacent apertures. Fourthly, half of the total number of recesses and projections circumferentially disposed about each aperture of the insulator must fall within a arc defined on either side of an imaginary line drawn through the centers of the adjacent apertures.

In a second embodiment depicted in FIGS. 5-7, an insulator 30 is constructed to provide an interlocking relationship between an interleaved stack of insulators and switch contacts to form a switch pileup of the type depicted in FIG. 4.

Each of the insulators 30, with the possible exception of the top and bottom ones, has a plurality of arcuate segments in the form of recesses 33 and projections 35 circumferentially disposed about each aperture 37 formed in the insulator. As in the case of the insulator l0 depicted in FIGS. l4, the recesses 33 and projections 35 are alternately arranged about the periphery of each aperture. However, the insulator 30 of the second embodiment, as well as other similar insulator arrangements which utilize an even number of recesses and projections, respectively, circumferentially disposed about each of two or more apertures, distinguishes in a number of particulars over the first embodiment when constructed to provide a symmetrical interlocking relation in a switch pileup. First, the recesses 33 and the projections 35 must not only be alternately arranged about the periphery of each aperture, as previously noted, but the recesses and projections,respectively, must be mutually disposed in pairs with respect to each other about an associated aperture on the same side of the insulator. Secondly, the pattern or orientation of recesses and projections associated with the respective apertures must be identical relative to a common reference line, such as one drawn through the axis of the centers of adjacent apertures. Thirdly, no recesses or apertures can be disected by a line drawn either through the axis of adjacent apertures or perpendicular to the first-mentioned line.

A notch or semicircular slot 39 separates each arcuate recess from an adjacent projection about the periphery of each aperture. These notches are employed both to facilitate the construction of the tooling involved in the molding apparatus employed to manufacture the insulators, and to permit the utilization of a manual stacking fixture designated generally by the reference numeral 45.

In all other respects, the insulator 30 functions in the same manner as the insulator l0, and exhibits the same advantages described hereinabove with respect thereto,

With respect to the stacking fixture, it comprises a base portion 46 and two mutually disposed U-shaped wall members 47. Two fin-shaped members 48 are secured to the base 46 and are respectively aligned with a different aperture 37 formed in the insulators and contacts. The fins are dimensioned such that the longitudinally extending ends 48a thereof fit loosely within the semiannular notches 39 of the insulators. Such a fixture may often be advantageously used to stack an interleaved array of switch contacts and insulators of rather small dimensions, and on a volume basis not warranting automated mechanism.

F l6. 8 illustrates a further embodiment in accordance with the principles of the present invention wherein an insulator 50, preferably of molded plastic material, has a plurality of alternately and circumferentially disposed recesses 51 and projections 52 of essentially semicircular configuration formed about apertures 53 of the insulator. These recesses and projections, of course, provide the same symmetrical interlocking features that are exhibited by the arcuate segments depicted in FIGS. 1-4 and 5-7. The substantially semicircular eonfiguration of the recesses and projections, could, of course, be displaced from the periphery of the apertures to such an extent that they could actually be formed as cylindrical recesses and projecting cylindrical studs or pins if desired. Should such recesses and projections be spaced apart, however, there would not be a continuous annulus-type wall or collar of plastic material isolating the peripheral walls defining the apertures in the spring contacts from the fastening members employed to hold the switch pileup together. This normally would not present a problem, however, as the peripheral walls defining the apertures in the switch contacts would generally be displaced from the peripheral walls defining the apertures 53 in the insulator by the radial distance across the recesses and/or projections.

As an odd-number of essentially semicircular recesses 51 and 52 are depicted in the insulator 50 of HO. 8, they would be positioned about the apertures in accordance with the criteria set forth he reinabove in connection with the description of the odd-number of arcuate recesses and projections, respectively, disclosed in the embodiment depicted in FIGS. 14.

We claim:

1. A composite pileup comprising:

a plurality of first members, each having at least one aperture therein; and

a plurality of second members, formed of nonconducting material, interposed between said first members, each of said second members having at least one aperture therein, with at least certain of the apertures in said first members and in said second members being axially aligned when stacked, each of said second members further including a plurality of interlocking recesses and projections alternately and circumferentially disposed about each aligning aperture therein, the relationship between the number of recesses and projections and their orientation being chosen and arranged, respectively, such that each second member is symmetrical from an interlocking standpoint when stacked with at least one other second member.

2. A switch pileup comprising:

a plurality of contact springs, each having at least one aperture therein, and

a plurality of insulators, formed of nonconducting material,

interposed between said contact springs, each of said insulators having at least one aperture therein, with the apertures in said contact springs and said insulators being axially aligned when stacked to form a switch pileup, each of said insulators further including a plurality of interlocking recesses and projections alternately and circumferentially disposed about each aperture on both sides of at least all of said insulators intermediate the top and bottom ones, the relationship between the number of recesses and projections and their orientation when more than one aperture is formed in an insulator being dependent on the particular number of projections and recesses, respectively, which surround each aperture on a given side of the insulator, the pattern of recess and projections formed being chosen such that each insulator is symmetrical, from an interlocking standpoint when stacked with at least one other of said insulators. 3. A switch pileup in accordance with claim 2 wherein when there are at least two apertures in each insulator, and when an odd number of recesses and projections, respectively, are disposed about each aperture on a given side of said insulator, each of said recesses is diametrically opposite a different projection on the same side of said insulator.

4. A switch pileup in accordance with claim 2 wherein when there are at least two apertures in each insulator, and when an even number of recesses and projections, respectively, are disposed about each aperture on a given side of said insulator, each recess and each projection is diametrically opposite a different recess and projection, respectively, on the same side of said insulator.

' 5. A switch pileup in accordance with claim 3 wherein said insulators are of molded plastic material, wherein said recesses and projections associated with each aperture are arranged such that half of the total number of recesses and projections circumferentially disposed about an associated aperture on-a given side of said insulator are positioned to fall on either side of an imaginary line drawn through the axis of at least the two adjacent apertures formed in said insulator, and wherein a recess and diametrically disposed projection associated with each aperture on the same side of said insulator are each disected by a second imaginary line drawn through the axis of the associated aperture and perpendicular to said first-mentioned imaginary line.

6. A switch pileup in accordance with claim 3 wherein said insulators are of molded plastic material, wherein said recesses and projections associated with each aperture are ar ranged such that half of the total number of recesses and projections circumferentially disposed about an associatedaperture on a given side of said insulator are positioned to fall on either side of an imaginary line drawn through the axis of at least the two adjacent apertures formed in said insulator, and wherein half of said recesses and projections associated with each aperture on the same side of said insulator likewise fall on either side of an imaginary line drawn through the axis of each associated aperture and perpendicular to said firstmentioned imaginary line. 

1. A composite pileup comprising: a plurality of first members, each having at least one aperture therein; and a plurality of second members, formed of nonconducting material, interposed between said first members, each of said second members having at least one aperture therein, with at least certain of the apertures in said first members and in said second members being axially aligned when stacked, each of said second members further including a plurality of interlocking recesses and projections alternately and circumferentially disposed about each aligning aperture therein, the relationship between the number of recesses and projections and their orientation being cHosen and arranged, respectively, such that each second member is symmetrical from an interlocking standpoint when stacked with at least one other second member.
 2. A switch pileup comprising: a plurality of contact springs, each having at least one aperture therein, and a plurality of insulators, formed of nonconducting material, interposed between said contact springs, each of said insulators having at least one aperture therein, with the apertures in said contact springs and said insulators being axially aligned when stacked to form a switch pileup, each of said insulators further including a plurality of interlocking recesses and projections alternately and circumferentially disposed about each aperture on both sides of at least all of said insulators intermediate the top and bottom ones, the relationship between the number of recesses and projections and their orientation when more than one aperture is formed in an insulator being dependent on the particular number of projections and recesses, respectively, which surround each aperture on a given side of the insulator, the pattern of recess and projections formed being chosen such that each insulator is symmetrical from an interlocking standpoint when stacked with at least one other of said insulators.
 3. A switch pileup in accordance with claim 2 wherein when there are at least two apertures in each insulator, and when an odd number of recesses and projections, respectively, are disposed about each aperture on a given side of said insulator, each of said recesses is diametrically opposite a different projection on the same side of said insulator.
 4. A switch pileup in accordance with claim 2 wherein when there are at least two apertures in each insulator, and when an even number of recesses and projections, respectively, are disposed about each aperture on a given side of said insulator, each recess and each projection is diametrically opposite a different recess and projection, respectively, on the same side of said insulator.
 5. A switch pileup in accordance with claim 3 wherein said insulators are of molded plastic material, wherein said recesses and projections associated with each aperture are arranged such that half of the total number of recesses and projections circumferentially disposed about an associated aperture on a given side of said insulator are positioned to fall on either side of an imaginary line drawn through the axis of at least the two adjacent apertures formed in said insulator, and wherein a recess and diametrically disposed projection associated with each aperture on the same side of said insulator are each disected by a second imaginary line drawn through the axis of the associated aperture and perpendicular to said first-mentioned imaginary line.
 6. A switch pileup in accordance with claim 3 wherein said insulators are of molded plastic material, wherein said recesses and projections associated with each aperture are arranged such that half of the total number of recesses and projections circumferentially disposed about an associated aperture on a given side of said insulator are positioned to fall on either side of an imaginary line drawn through the axis of at least the two adjacent apertures formed in said insulator, and wherein half of said recesses and projections associated with each aperture on the same side of said insulator likewise fall on either side of an imaginary line drawn through the axis of each associated aperture and perpendicular to said first-mentioned imaginary line. 